It almost seems quite amazing, but given modern pollution laws as well as the advancement of fine quality four stroke motorbike engines that the old two stroke engine design still endures today. Yet, the modern two stroke engine remains as a powerful workhorse for many smaller displacement motorbikes, turning out fine power and torque for the size of engine. And since two stroke engines fire once per engine revolution, there is always the potential of a power output twice that of a similarly sized four stroke design. My little 2008 Benelli is a pretty good example of a modern two stroke motorbike. For the small 50cc engine size, the bike can nearly top 50mph. And it has great pickup. There is an automatic oil feed system that avoids having to mix oil and fuel. Yet for good reason the two stroke engine designs remain a subject of great controversy.
One of the biggest problems associated with the two stroke engine is the higher pollution levels they create. Two stroke engines must use oil in the gas in order to survive, and all produce at least some oil smoke. Especially in Europe, the two stroke designs have become a threatened species as air pollution rules tighten up. Yet fans of two stroke bikes of all types, both motorcycles and scooters, seem to have at least some new two stroke models survive. Even in the U.S., the EPA continues to allow more efficient two stroke motobikes to be sold, however in the future that could all change. However, at some point in the future, new two stroke engines motorbikes are very likely to become an endangered species, much to to the sadness of many motorbike fans.
Before 2006, motobikes with an engine displacement of 50cc or less were exempt from EPA certification. However, since 2006, all motorbike engines that are two stroke must be tested and certified by the EPA. This has made it more difficult for many two stroke models to be imported into the U.S., and probably explains why the 50cc CPI GTR, which has a sport bike type design body and a two stroke engine is no longer imported here. But the four stroke 180cc version is still available. The CPI GTRs are a real popular cult item throughout Europe and Asia, and on Youtube, many videos exist of fans showing off their bikes.
Yet, part of the appeal of the two stroke engine is the unique sound they create, the extra power as well as the smell of the engine. Two stroke engines have an appeal to a motorhead cult of motorbike followers. At one time some automobiles such as Saab actually used two stroke engines in their automobiles as well.
The two stroke is also a simple design to create. There are no valves. However, generally speaking, two stroke engines do not live as long as four stroke engines by any means. However, some pretty good synthetic engine oil on the market will extend the life of a two stroke considerably. However, the four stroke design has many advantages such as better fuel economy and a quieter sound. But since the four stroke only creates power on every other revolution due to the design where intake and exhaust valves must open and close, it may take an engine twice the size of a two stroke one to produce the same level of power. In some 50cc motorbike racing for example, some two strokes can exceed 130km(80mph)an hour, which is an unheard of speed for a similar sized four stroke engine.
And two stroke engines remain a popular design in some yard equipment as well as chainsaws because of the greater power they produce as well. However, as the EPA and other environmental watchdogs become more mindful of the state of the environment as well as growing concerns over global warming my best guess is that the future days of the two stroke might well be numbered. Little doubt in my view that these old style engines with such a simple design , that may not be very fuel or pollution efficient will someday be banned from production by law.
Two stroke engine fans need to enjoy these bikes while they're still here.
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